Ancient-Red-Dragon: ...Except that sort of thing is exactly what GOG has
already been doing, and the many years for which GOG has been doing that has proven that that approach doesn't work, and therefore, year after year, GOG always receives very few premium quality top tier games.
OP's proposal is a new approach towards correcting that problem. It certainly isn't going to correct itself if GOG keeps doing nothing other than to keep doing things in the same way as they always already have been.
This is predicated on the assumption that
1) Publishers want to publish on GOG and the only thing holding them back is DRM-free
2) Publishers (especially AAA) are willing work to remove DRM-related software from games after a certain period of time
I think 1 already has some flaws. All of the Playstation on PC games (Days Gone, God of War, HZD, Spiderman) are DRM-free on Epic and steam-DRM only on steam but still didnt make their way to GOG. Other notable indie games like Hades are also apparently DRM-free but have not come to GOG.
I dont think that its only DRM-free requirement a blocker (I do think it is for some big studios like EA or Square Enix) but also the simple fact that GOG just doesnt have as much market share.
Its a sad but simple fact that steam owns about 75% of the PC gaming market. Indie developers likely feel they can reach most of the market, fan interactions, updates, etc by just focusing on steam as the benefits from going to other storefronts is likely marginal. Epic is only making waves right now because they are far more generous in their cut and contracts but in terms of market share, Steam still dominates.
Since GOG doesnt have the market share of steam (and maybe has lost to Epic) or the money of Epic, its going to be hard for GOG to attract more games which puts GOG in his vicious negative cycle (no new games so no new customers so no new developer interest so no new games...) and becoming "steam-lite" wont change that. If anything, it will cause current GOG customers to leave while current steam users wont transition to GOG (because "hur hur everyone wants to copy steam but steam already da best" in their minds).
It also doesnt help that the majority of consumers arnt informed enough to realize what DRM means and how little ownership they actually have over recent products. There are still people "surprised" by the fact that they lose access to movies they "bought" on their Prime subscription of the movie is delisted from the Prime service and since steam is so big, there is the assumption that "well as long as steam doesnt close down my library is fine and steam will never close"